Slot closer for dynamoelectric machines



Oct. 19 1948. A. E. B. PERRIGO SLOT CLOSER FOR DYNMOELECTRIC MACHINES Filed NOV. 15, 1947 Patented Oct. 19, 1948 SLOT CLOSER FOR DYNAMOELECTRIC MACHINES Albert Edward Bell Perrigo, Walsall, England, assignor to H. Frost and Company Limited, Walsall, England, a company of Great Britain Application November 15, 1947, Serial No. 786,180 In Great Britain May 31, 1947 9 Claims.

This invention relates to dynamo-electric machines, such as induction motors, having stators or rotors provided with initially-open windingreceiving slots separated by pole teeth and which are closed, after the windings have been introduced, by means of closure strips or bars.

Whilst fully-open slots between the teeth or poles of the stator or rotor enable the windings to be readily inserted, as, for example, when former-wound coils are used, the ux distribution in the air gaps between the teeth is not so eiiciently distributed as with partially-closed slots when closure members composed entirely of non-magnetic material are used.

The object of the present invention is to enable the reluctance of the iiux leakage path across adjacent teeth to be controlled to a value which will give the most efcient flux distribution in the air gaps, so that a machine with open slots can be made to give a, performance substantially equal to that given by a corresponding machine having partially-closed slots.

According to the invention, in a dynamo-electric machine having coils in open slots, the slots are closed by strips or bars of composite unitary construction comprising separate longitudinal side members made of magnetic material in direct contact with the pole teeth and an intermediate longitudinal portion of non-magnetic material which connects together and spaces apart the side members so as to form therewith a self-contained unit.

Figure 1 of the accompanying drawings is a fragmentary elevation of the inside face of a portion of the stator of an induction motor having slot-closing means in accordance with the present invention.

Figure 2 is a, cross-section through two of the teeth and the closure strip between them, on a larger scale, the section being taken on a plane corresponding to line II-II, Figure 1.

Figure 3 is a similar sectional view of a modication.

Figure 4 is a section showing another modilcation.

Figure 5 is a section showing a further modification.

Referring to Figures 1 and 2 of the drawings, which illustrate one form of the invention in connection with the stator of an induction motor, the said stator has initially-open coil-receiving slots l formed between the side walls of parallel-sided pole teeth 2 by the axial alignment of corresponding slots formed in the laminations of which the stator is formed. In the (Cl. Pil-252) opposite side walls of these coil slots, at a short distance inwards of the open ends, longitudinal grooves 3 are provided, and after former-wound coils 4 of round wire, or other windings, have been introduced into the open slots, the latter are closed by means of closure strips or bars which are slid endwise into the grooves in the side walls of the slots. Each of these strips or bars consists of two separate longitudinal side members 5, 5, made of magnetic material connected together and spaced apart, to form a selfcontained unit strip, by a longitudinal intermediate rigid portion 6 of non-magnetic material.

The side members 5 are in the form of sheetmetal strips or pressings. They are of a doubleangle or cranked section, with outwardly presented set-back longitudinal flanges, and inwardly-presented flanges at the front. The two strips 5, 5, are spaced apart, with their front flanges in alignment but spaced apart, and they are joined together by the intermediate non-magnetic material 6. This material may be a suitable plastic which is moulded upon and bonded to the side members 5 so as to fill up the hollow space between the two members ush with the set-back outwardly-presented flanges, and also so as to fill up the air gap or space between the opposed edges of the front flanges, flush therewith. The plastic material may be held and bonded to the metallic side members by providing the latter with struck-up keying lugs I which are embedded in the plastic material. A self-contained closure strip or bar of unit construction is thus provided, and it can be slid endwise into the grooves 3 of the teeth by means of its outwardly-presented ilanges, which are in direct contact with the teeth 2. When in position the strips interlock with the teeth and the front flanges of the side members are substantially flush with the outer faces of the teeth.

According te a modification shown in Figure 3, each closure strip unit comprises two laterallyspaced metallic side members 8, 8, of magnetic material, each of hook-like section comprising a short front straight portion and an integral outwardly-bent part 9 of U-section forming an outwardly-presented flange and an inwardly-presented groove. The two members are located in opposed relation and spaced apart, with the groove of one opposed to the groove of the other; and they are connected together by pastic material lll moulded into the space between them so as to ll up said space, including the grooves and the spacing gap at the front, said material being then flush with the front and rear surfaces of antibes the metal members. A strip of unit construction -is thus formed, which can be engaged between adjacent teeth 2 by sliding the outwardly-presented flanges into the grooves 3 of the teeth, the outer face of the strip being then substantially flush with the end faces of the teeth. Struck-up keying lugs Iii may be provided on the side members for embedding in the plastic material.

In another modification, shown in Figure 4, two metal side members I2 of magnetic material are of similar hook section to those last described, but they are positioned and laterally spaced with the bends of the U-shaped portions I'3presented forwardly, the straight port-ions Yprojecting laterally to form outwardly-presentedflanges They are Iconnected together, to .form a unit strip, by plastic material M moulded "into 'the space between them and into the hollows of the U-portions, flush with the front and rear surfaces. vThe outwardly-presented flanges are inserted into the grooves 3 of Vthe 'teeth 2 so that :the-iront faces of the-strips are Hush with the end faces of the teeth.

Again, in a further modification, :represented in `lfigur'e .5, the composite closure'strips'may comprise two laterally-spaced metal side members l5 .of magnetic material each 4o J -section, but mutually .-reversed, the y'hook portions` I6 being at the irontand being opposed laterally. These members are .inclined outwards ltowards their rear ends, Aand `the space between `them is iilled with plastic material I-l flush with the front and rear ends, `thesaid material filling the Ihook 'portions andalso the A(airg'ap between the Vhook portions, beinghonded kto the side members lto form a selfcontainedduni-t of dovetailor wedge section. VThis unit is .adapted -to be slid endwise into interlocking engagement with dovetail Vrecesses |18 formed in oppositel .faces vof adiacentA teeth -2, so that the front nof the strip `is iiush with the4 end .-faces of Inail y.cases/the spacing of Vthe magnetic side members and .the 'material :of which they are vformed is .s 'o'chosen thatthe reluctance -of the magnetic .leakage'pathbetween 4adjacent stator teeth is controlled to giveathe most .efficient flux distribution. f lclaim.: n `l. VA dynamo-electric machine having -open coil-'receivingv slots between atcfijacent pole teeth, in `combination with coils in the slotsjand compositeslot-.closing 'strips of Vunit construction-comprising separate longitudinal side members of magnetic material indirect contact with the pole teeth land .an intermediate'longitudinal-portion of non-magnetic Ymaterial which lconnects `and spaces theside 'members :to form therewithaseli- 'cintalinedunit y Y Y '2. A .dynamo-electric machine having =open coil receiving slots between adjacent pole-teeth, in combination with coils -in the slots and composi'te slot closing strips Vof unit construction comprising .separate longitudinal side' members of i. ginietic material and an intermediate longitudinal portionV of nonmagnetic material which connects and spaces the side members toV form a self-,contained unit, the rear portions of the side members vextending laterally rbeyond the `front portions and interlocking with adjacent pole teeth so'fthat Vtheffront faces of Vthe strips are substantially flush with theend faces ofthe teeth.

3.'A vrd'ynam'o-.electric machine having openv cileregceiving' slotsbetween adjacent pole teeth, in combination with coils vin 'the slots and com- 4 posite slot-closing strips of unit construction coniprising separate longitudinal side members of magnetic material and an intermediate portion of non-magnetic material which connects and spaces the side members, said side members having .set-back outwardly-.extending anges' engaging grooves in the side portions *of :the teeth so that the front faces of the strips are substantially flush with the end faces of the teeth'.

4. A dynamo-electric machine having open coil-receiving slots between adjacent pole teeth, in combination with coils in the slots and com- -posite'slot-closing strips of unit construction comprising two separate longitudinal side members of magnetic material pressed to a section having set-back outwardly-presented flanges engaged with the teeth, said side members being connected by and bonded to an intermediate filling of nonmagnetic material moulded within the space between said side members.

5. A dynamo-electric machine `vhaving .open coil-receiving slots between adjacent ',-pele teeth, in combination with coils in the slots and composite 'slot-closing strips vcomprising side Imembers-of magnetic material having a cranked seetion forming set back outwardly extending flanges engaging grooves-in the teeth, `said members being connected by an intermediate portion of non-magnetic material which holds the said members in spaced relation and-forms a closure strip of unit construction.

6. vA dynamo-electric machine `having open coil-receiving slots between pole teeth, in'eombination with coils in the slots and composite-slotclosing strips comprising separate longitudinal side members of magnetic material and of avbent hook section with' outwardly-presented set-back flanges, said -side members being connected :by and bonded to an intermediate member of nonmagnetic materiallmoulded in the space .between the side members Yso as-to hold the latter together in spaced relation andform a.self-contained unit.

7. A dynamo-electric machine :having open coil-receiving slots between `adjacent poleteeth, in combination with coils in Athe-slotsand composite slot-closing strips comprising separate longitudinal sidemembersY-of J-section disposed in reversed relation and spacedv apartfand an intermediatelling of non-magnetic :material moulded between the sidefmembersso as vto connect-and space Vthe same and forma -unit .closure strip fof dovetail section.

8. Acompositestr-ip for closing =fa coil-receiving slot of a dynamo-electric Amachine vcomprising separate Alongitudinal side members made of -magnetic material and -an `intermediate longitudinal portion of non-magnetic material which connects and yspaces th'esid'e memberstoform a self-containedrunit, the said side members having Aoutwardly-extending angfe parts-setback from-one face of the strip.

:9. A compositestrip for closing a coil-receiving slot of a dynamo-electric machine comprising separate `longitudinal side member-s madeof magnetic sheet material fashioned to a section-which provides outwardly-.extending flanges setback from one face of the strip, in combination withan intermediate filling of non-magnetic material moulded within .the yspace betweenthe side members and ser-ving vto-corinect and space said-members `to Iproduce -a self-contained -unit strip.

ALBERT EDWARD `BELL PERRIGG.

`Noireferences cited. 

